Production of higher olefins

ABSTRACT

A method of making a higher olefin product from a C 4   +  fraction separated from the hydrocarbon product produced by an oxygenate to olefin reaction unit. The C 4   +  fraction primarily contains butenes which may be directed to a higher olefin reaction unit without removing isobutenes, butanes, and/or butadiene. The C 4   +  fraction is particularly well suited for the production of higher olefins because of its high olefin content, low branching number, and low contaminent levels. The invention is also directed to an olefin product composition that is produced by contacting the C 4   +  fraction with an oligomerization catalyst. The olefin composition is characterized by a relatively high octene content, and octene with a branching number less than 1.4.

[0001] This application claims priority to U.S. Provisional PatentApplication No. 60/265,700, filed Feb. 1, 2001.

FIELD OF THE INVENTION

[0002] This invention relates to a system of making olefin derivatives,namely higher olefin, from olefin produced from an oxygenate. The higherolefin may then be used to produce a variety of olefin derivativeproducts including alcohols, aldehydes, acids and esters.

BACKGROUND OF THE INVENTION

[0003] Olefins such as butenes and pentenes are useful in preparing awide variety of derivative end products. Examples of such end productsinclude alcohols, aldehydes acids and esters. The butenes and pentenescan also be oligomerized to form higher olefins having eight or morecarbons. The higher olefins may be linear or they may have one or morealkyl branches. The higher olefins can then be converted to alcohols,aldehydes, acids and esters.

[0004] Butenes used in preparing olefin derivative products aretypically made by cracking hydrocarbon feedstocks, i.e., producing lowmolecular weight hydrocarbons from high molecular weight hydrocarbons.Cracking of hydrocarbon feedstocks can be accomplished catalytically ornon-catalytically. Non-catalytic cracking processes are described, forexample, in Hallee et al., U.S. Pat. No. 3,407,789; Woebcke, U.S. Pat.No. 3,820,955, DiNicolantonio, U.S. Pat. No. 4,499,055 and Gartside etal., U.S. Pat. No. 4,814,067. Catalytic cracking processes aredescribed, for example, in Cormier, Jr. et al., U.S. Pat. No. 4,828,679;Rabo et al., U.S. Pat. No. 3,647,682; Rosinski et al., U.S. Pat. No.3,758,403; Gartside et al., U.S. Pat. No. 4,814,067; Li et al., U.S.Pat. No. 4,980,053; and Yongqing et al., U.S. Pat. No. 5,326,465.

[0005] One problem with using a hydrocarbon cracking unit to produceolefins is that the olefins contain a significant degree of alkylbranched olefin. For example, in a butenes stream, isobutene must firstbe removed before the butenes are directed to an oligomerization unit.The presence of isobutene in the butenes feed will result in branchedhigher olefin, which leads to branched alcohols. Branched alcohols haverelatively little commercial value because they result in inferiorplasticizers.

[0006] Another problem with olefin produced by a hydrocarbon crackingunit is that the olefin contains significant quantities of sulfur andnitrogen compounds. These compounds deactivate the acidic catalysts usedin olefin derivative processes, such as olefin oligomerization. Forexample, Bodart, U.S. Pat. No. 5,432,243, and Debras et al., U.S. Pat.No. 4,861,939, disclose that arsine and carbonyl sulfide (COS) can beproblematic in the olefin derivative process unless the contaminants areremoved by additional purification equipment. U.S. Pat. No. 5,146,042 toGurak et al. suggests that sulfur contaminants in C₂ to C₄ olefin canlead to undesirable side reactions in higher olefin and olefinderivative processes. Purification of such olefin requires that thecontaminants be extracted into selected hydrocarbons followed by thedistillation of the cleaned, lighter olefin from the hydrocarbons.Alternatively, nickel catalysts can be used to remove the sulfurcontaminants. The equipment required to remove sulfur from an olefin isgenerally quite large in scale and quite expensive to operate.

[0007] Additional separations, such as diene removal, iso-alkeneremoval, and/or paraffin removal may be required depending upon thehydrocarbon source used in the cracking unit. As an example, the butenesstream from a hydrocarbon cracking unit contains significant amounts ofbutadiene and isobutene that must be removed. In U.S. Pat. No. 6,049,017to Vora et al., the butadiene is removed by a controlled hydrogenationprocess. The isobutene is removed catalytically by contacting thebutenes stream with methanol in a methyl-t-butylether (MTBE) reactor.The isobutene is converted to MTBE and the normal butenes and butanepass through the MTBE reactor. The normal butenes and butanes are thendirected to a butane cracking unit to produce ethylene and propylene orto an oligomerization unit.

[0008] Generally, in the production of higher olefin, butanes are notremoved from the butenes stream because a once through or low recyclehigher olefin process is used. Instead, butanes are separated from thehigher olefin product, which is a much easier and less costlyseparation. For example, the olefin content of a butenes stream from asteam cracking unit is typically about 60% by weight. The butenes streamis directed to the higher olefin unit at a conversion per pass of about50% to 70%. There is little or no recycle, and the butanes are easilyseparated from the higher olefin product. However, there are severaldisadvantages to this process. One, 30% to 50% of the olefin in the feedis not converted to the desired product resulting in overall low processyields. Two, the high conversion per pass process results in a lowerselectivity to the more desirable alpha-olefins. Alpha-olefins areolefins that contain the carbon-carbon double bond between the first andsecond carbon.

[0009] A high recycle, low conversion per pass process may address bothof these disadvantages, however, such a process requires theavailability of an olefin stream with a high olefin content to maintainthe olefin concentration in the feed at an acceptable level. A butenesstream from a cracking unit, has a low olefin content. Consequently, asignificant portion of the paraffins must be removed from the butenesstream if a high recycle, low conversion per pass process is to be used.This removal process can be a difficult and expensive task because ofthe relatively close boiling ranges of the components.

[0010] Removing various chemical contaminants from an olefin stream forproducing an olefin derivative product can be a technically difficultprocess depending upon the feed specifications for the process.Therefore, if one could minimize or avoid the paraffin and contaminantremoval process by having available an olefin stream with low levels ofparaffin, alkyl branching, diene, and/or contaminant levels the costs ofremoving these components would be minimized or eliminated altogether.

SUMMARY OF THE INVENTION

[0011] The invention provides a method of making a higher olefinproduct, particularly a mixture of octenes, nonenes, and dodecenes fromolefin produced from an oxygenate to olefin process. The method includescontacting an oxygenate with a molecular sieve catalyst to produce ahydrocarbon product containing olefin, separating a C₄ ⁺ fractioncontaining four or more carbons from the hydrocarbon product, andcontacting the C₄ ⁺ fraction with an oligomerization catalyst to producea product containing higher olefin. Optionally, a portion of theunreacted olefin that was not converted to product can be directed backto the C₄ ⁺ fraction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] This invention will be better understood by reference to theDetailed Description of the Invention when taken together with theattached drawings, wherein:

[0013]FIG. 1 is one embodiment for making a higher olefin;

[0014]FIG. 2 is one embodiment for separating the higher olefin productinto various olefinic components.

DETAILED DESCRIPTION OF THE INVENTION

[0015] In order to reduce the associated costs of producing higherolefins, this invention uses a portion of a hydrocarbon product from anoxygenate to olefin unit to make a novel hydrocarbon C₄ ⁺ fraction.Preferably, the oxygenate to olefin unit is a methanol-to-olefin (MTO)unit. This C₄ ⁺ fraction contains greater than 60% by weight, preferablygreater than 80% by weight, C₄ ⁺ olefin. The C₄ ⁺ fraction contains arelatively high olefin content, i.e., low amounts of paraffin, verylittle diene, and relatively low degree of branched olefin. In theinvention an olefin stream with greater than or equal to about 60% byweight olefin is referred to as an olefin stream having a high olefincontent. Conversely, an olefin stream with less than about 60% by weightolefin is referred to an olefin stream having a low olefin content.Also, the C₄ ⁺ fraction contains relatively little or no sulphur andnitrogen compounds that tend to deactivate oligomerization catalystsused in a higher olefin process.

[0016] This invention provides a higher olefin product containingsignificant amounts of octenes, nonenes, and dodecenes. The higherolefin can then be used to make higher alcohols, which may be used as achemical feedstock for a number of commercial plasticizers. The processoffers the advantage in that relatively expensive olefin purificationequipment need not be used, or if used, smaller purification units areneeded when the desired C₄ ⁺ fraction is used. In large commercial scaleprocesses, this results in a significant reduction in equipment costs aswell as a significant reduction in operation costs. This reduction inequipment and operation costs ultimately provides the consumer with aproduct of the same high quality, but at significantly less cost.

[0017] In this invention, a hydrocarbon product from an oxygen to olefinreaction unit is directed to separation units, known in the art, toseparate hydrocarbons according to carbon numbers. For example, methaneis separated from the hydrocarbon product followed by, ethylene andethane (C₂ separation), then propylene and propane (C₃ separation). Theremaining portion of the hydrocarbon product, namely the portioncontaining predominantly four and five carbons (C₄ ⁺ fraction), isdirected to a higher olefin unit. Alternatively, the C₄ ⁺ fraction canbe separated in the beginning of the separation sequence to reduce thecapacity requirements of the C₂/C₃ separation unit by as much as 10% to25%.

[0018] The C₄ ⁺ fraction contains greater than 60% by weight, preferablygreater than 80% by weight, more preferably greater than 90% by weight,hydrocarbon having four and five carbons. The C₄ ⁺ fraction containsgreater than 60% by weight, preferably greater than 80% by weight,olefin having four carbons (C₄ olefin). Examples of olefin contained inC₄ ⁺ fraction are 1-butene, cis and trans 2-butene, isobutene, and thepentenes. The C₄ ⁺ fraction preferably contains from 60% to 97% byweight, preferably 80% to 97% by weight, olefin. The remainder of the C₄⁺ fraction contains paraffin and small amounts of butadiene and othercomponents. It is desirable that the C₄ ⁺ fraction will more preferablyhave a compositional range as follows: 70% to 95% by weight, morepreferably 80% to 95% by weight, normal butenes, which includes 1-buteneand cis and trans 2-butene; 2 to 8% by weight, preferably less than 6%by weight, isobutene; 0.2% to 5% by weight, preferably less than 3% byweight butanes; 2% to 10% by weight, preferably less than 6% by weight,pentenes; and 2% to 10% by weight, preferably less than 5% by weight,propane and propylene.

[0019] It is also desired that the olefin C₄ ⁺ fraction have a lowbranching number. It is desirable that the average branching number beless than 2.0, preferably less than 1.6, more preferably less than 1.4.The Average Branching Number (ABN) is defined as:

ABN=1+(1*% monobranch+2*% dibranched)/% total olefin

[0020] For example, if a dilute olefin stream has 20% 1-butene, 50%2-butene, 10% butane, 10% isobutene, 5% propane, and 5% 3-methylbutene,the average branching number is about 1.17. An olefin having near 0%branched olefin will have a ABN of about 1.0.

[0021] In one embodiment, the C₄ ⁺ fraction can be used as is, that is,directly from the separation unit to the higher olefin unit.Alternatively, there can be some further processing of the C₄ ⁺ fractionbefore directing it to the higher olefin unit if desired. This mayinclude a hydrogenation process that would selectively hydrogenate mostif not all of the butadiene to butenes and a portion of the isobutene toisobutane. It is also important to limit the amount of isobutene in theolefin feed to minimize the amount of branched higher olefin product.Preferably, the C₄ ⁺ fraction is directed to the higher olefin unitwithout butadiene or isobutene removal.

[0022] In another embodiment, purification of the C₄ ⁺ fraction mayrequire removal of low level impurities which will interfere with higherolefin reaction unit performance, and/or oxo (hydroformylation) catalystperformance. Low level contaminants will generally comprise polarmolecules. Examples include oxygenates such as water, ethers, alcohols,and carboxylic acids. These compounds can be removed with variousmaterials, such as solid molecular sieves, extraction with varioussolvents, and fractional distillation.

[0023] The C₄ ⁺ fraction is typically low in contaminants such ashydrogen sulfide, carbonyl sulfide, and arsine. As a result, the C₄ ⁺fraction can be directed to a higher olefin unit with minimal separationand purification. In fact, following separation of the C₄ ⁺ fractionfrom the oxygenate to olefin hydrocarbon product, removal of hydrogensulfide, carbonyl sulfide, or arsine is often not necessary. Desirably,C₄ ⁺ fraction will have a hydrogen sulfide content of less than 20 partsper million by weight (ppmw), preferably less than 5 ppmw., morepreferably less than 1 ppmw. It is also desirable that C₄ ⁺ fractionhave a carbonyl sulfide content of less than 20 ppmw, preferably lessthan 5 ppmw., more preferably less than 1 ppmw. Likewise, it isdesirably that C₄ ⁺ fraction have an arsine content of less than 20ppmw, preferably less than 5 ppmw, more preferably less than 1 ppmw.

[0024] Should additional purification of the olefin product stream beneeded, purification systems such as that found in Kirk-OthmerEncyclopedia of Chemical Technology, 4th edition, Volume 9, John Wiley &Sons, 1996, pg. 894-899, the description of which is incorporated hereinby reference, can be used. In addition, purification systems such asthat found in Kirk-Othmer Encyclopedia of Chemical Technology, 4thedition, Volume 20, John Wiley & Sons, 1996, pg. 249-271, thedescription of which is also incorporated herein by reference, can bealso be used.

[0025] In another embodiment, the C₄ ⁺ fraction is directed to thehigher olefin unit without separating hydrocarbons of different carbonnumber, olefin from paraffin of like carbon number, or directing the C₄⁺ fraction to an MTBE unit to remove the isobutene or to a hydrogenationunit to remove butadiene and/or isobutene. As a result, dedicatedfacilities such as distillation units for separating C₄ from C₅hydrocarbons or the butenes from butane, an MTBE unit, and ahydrogenation unit are not required prior to directing the C₄ ⁺ fractionto the higher olefin unit.

[0026] In another embodiment, a portion of C₄ ⁺ fraction that is notconverted to product in the higher olefin unit is directed back to theC₄+fraction. As a result, the hydrocarbon feed to the higher olefin unitwill have a different compositional make-up than the C₄ ⁺ fraction. Thehydrocarbon feed to the higher olefin unit will include hydrocarbonsfrom a recycle stream, which will typically contain relatively moreparaffin than the C₄ ⁺ fraction. The compositional range of thehydrocarbon feed to the higher olefin unit depends upon the desiredspecifications of the higher olefin product, the oligomerizationcatalyst, the reaction conditions in the oligomerization unit, theamount of recycled hydrocarbon, and the composition of the C₄ ⁺fraction.

[0027] The low paraffin and contaminant content of C₄ ⁺ fractionprovides the operational flexibility of running a high recycle, lowconversion per pass higher olefin process. The invention allowsunreacted olefin from the higher olefin unit to be recycled withoutsignificantly adding to the overall load of the higher olefin unit andrecovery facilities and without significant risk of accumulatingcontaminants that may deactivate the olgomerization catalyst. By using afeed that is low in paraffin and low in harmful contaminants with ahigher olefin unit that utilizes a high recycle, low conversion per passprocess, the overall yield and isomer selectivity of the higher olefinproduct can be significantly increased. A high recycle, low conversionper pass higher olefin process can convert greater than 80%, oftengreater than 90%, of the olefin in the process. Also, the high recycleprovides greater operational flexibility to optimize the productselectivity to alpha-olefins, such as 1-octene.

[0028] In contrast, a conventional once through, high conversion higherolefin process will typically convert less than 80%, often less than70%, of the olefin in the process. Also, because the conventional higherolefin unit operates at a relatively high conversion per pass, theselectivity to a more desirable higher olefin product is lower. Desiredhigher olefin product will contain relatively higher amounts ofalpha-olefin and have a relatively low branching number.

[0029] A high recycle, low conversion per pass higher olefin processrequires the availability of an olefin feed with a high olefin contentto keep the purge volume to a minimum. In one embodiment, a C₄ ⁺fraction with a butenes concentration between 70 and 97% by weight isdirected to a higher olefin unit. The C₄ ⁺ fraction is mixed with thehydrocarbons from the recycle stream to produce an optimal hydrocarbonfeed composition to the higher olefin unit. The optimal hydrocarbon feedcomposition will vary depending upon the recycle and olefin conversionpercentages in the higher olefin unit. The hydrocarbon feed compositionmay vary between 20 to 95% by weight butenes. The paraffins are used asa diluent to control the rate of reaction in the higher olefin process.The low amount of paraffins in the C₄ ⁺ fraction also minimizes thevolume of purge gas needed to control the level of inerts in thehydrocarbon feed. This minimizes the amount of olefin lost in the purgestream.

[0030] The high recycle process will have an olefin conversion per passratio of between 30% and 70%, preferably between 40% and 70%, morepreferably between 45% and 70%. The total olefin conversion can be ashigh as 80% to 98%, preferably from 90% to 98%. Another advantage ofusing a high recycle, low conversion per pass process is that theproduct selectivity, e.g., the isomer selectivity to 1-octene, can beoptimized.

[0031] One embodiment of a high recycle process is shown in FIG. 1. C₄ ⁺fraction 12 produced in an oxygenate to olefin unit 10 is directed to ahigher olefin unit 14. The product 16 containing higher olefin andunreacted olefin and paraffins is directed to a product separation unit15. The higher olefin product 17, namely the octenes, nonenes anddodecenes, are separated from the unreacted olefin and paraffin, andthen directed to additional separation units. These separation units arerepresented as 15 b, 15 c, 15 d, and 15 e in FIG. 2. The vent stream 18contains unreacted olefin and inerts, including paraffins. The ventstream 18 comprises 40% to 90% by weight olefin. A portion of the ventstream 18 is removed via purge stream 22 to maintain the inerts balancein the higher olefin unit to a specific compositional range, which inturn maintains the olefins at the desired concentration in thehydrocarbon feed to the higher olefin unit 14. The remainder of the ventstream 18 is recycled to the olefin reaction unit 14 via recycle stream26.

[0032] Another embodiment includes removing at least a portion of theparaffin and undesirable olefin from the vent stream 18 using one ormore separation units. Examples of olefin separation units includefractional distillation equipment, including dephlegmators, andabsorption, extractive or membrane separation equipment, andcombinations thereof. Preferably, the olefin separation units are one ormore fractional distillation units. Preferably, the fractionaldistillation unit is operated without the use of a lean physicalsolvent. Example compounds removed from the vent stream 18 includebutane and isobutane. After a desired portion of such compounds havebeen removed as a purge stream, the desired separated olefins can berecycled to the higher olefin unit 14 via recycle stream 26.

[0033] Once the total amount of paraffins and olefin to the higherolefin unit 14 is set, the mass flow of vent stream 18 is determined bythe desired extent of removal of the paraffin and olefin through olefinpurge stream 22, and the recycle ratio in the process. In a preferredembodiment, at least 50% by weight of the paraffins in vent stream 18are removed through purge stream 22, more preferably at least 75% byweight, and most preferably at least 90% by weight. A greater percentageof paraffins will be removed if a separation unit is positioned in thevent stream 18. Preferably, purge stream 22 will comprise no more than50% by weight, more preferably no more than 20% by weight, and mostpreferably no more than 5% by weight, olefin.

[0034] Preferably the olefin recycle stream 26 comprises at least 50% byweight of the olefin contained in the vent stream 18, more preferably atleast 75% by weight, and most preferably at least 90% by weight. Thebalance of the recovered olefin stream 26 may comprise paraffins andother materials found in the vent stream 18.

[0035] Most if not all known processes known in the art can be used tooligomerize

[0036] C₄ ⁺ fraction to higher olefins having eight or more carbons.Solid phosphoric acid polymerization is the commonly used process forthe oligomerization of butenes. In the process the butenes are fed to amultibed reactor containing solid phosphoric acid, which is made from apelletized and calcined mixture of phosphoric acid on kieselguhr.Operating conditions are 175° C. to 225° C. and pressures of at least 20atm. The higher olefin selectivity is relatively poor, and for thisreason the process is often associated with petroleum refining to ensureeconomical use of the less value products. Also, the disposal of thecatalyst in landfills presents environmental issues and related costs.

[0037] Dimersol® is a commercial process that produces a more linearolefin than the phosphoric acid process. The reaction is carried out at50° C. to 80° C. and about 1600 kPa to 1800 kPa in the liquid phaseusing a homogeneous nickel-alkyl aluminum catalyst. Ammonia and waterare injected into the product stream to neutralize the catalyst, and thehydrocarbon is then separated from the aqueous phase. The catalyst isthen recovered and recycled back to the reactor.

[0038] In another embodiment, a modified ZSM-22 catalyst can be used asan oligomerization catalyst. U.S. Pat. No. 6,013,851 to Verrelst et al.,the disclosure of which is incorporated herein by reference, describes amodified ZSM-22 olefin oligomerization molecular sieve catalyst whereinthe molecular sieve contains a metal-silicon core and surface layer,with the surface layer having a higher silicon metal ratio than that ofthe core. The metal is selected from aluminum, gallium and iron. Thiscatalyst reduces the amount of branched higher olefin produced in theprocess. Also, the presence of some paraffin in the olefin feed has noor little effect on the catalytic efficiency of the catalyst. As aresult, the relatively small amounts of butane in C₄ ⁺ fraction does nothave to be separated from the feed. For example, a 1:1, preferably 2:1,ratio of butene:butane can be used. Small amounts of water are alsoshown to enhance the production of desired higher olefin.

[0039] Using the modified ZSM-22 catalyst in a high recycle, higerolefin process the product selectivity to octene is retained with adecrease in the amount of branching. For example, using C₄ ⁺ fraction asfeed, octene selectivity can exceed 80%. An octene selectivity greaterthan 90% can be achieved with a higher recycle ratio. Theoligomerization may take place at a temperature in the range of from160° C. to 300° C., preferably from 170° C. to 260° C., and mostpreferably from 180° C. to 260° C., at a pressure advantageously in therange of from 5 MPa to 10 MPa, preferably from 6 MPa to 8 MPa, and at anolefin hourly space velocity advantageously in the range 0.1 hr⁻¹ to 20hr⁻¹, preferably from 0.5 hr⁻¹ to 10 hr⁻¹, and most preferably 0.75 hr⁻¹to 3.5 hr⁻¹.

[0040] In another embodiment, the oligomerization of C₄ ⁺ fractionolefin can be carried out in the presence of a nickel oxide (NiO)catalyst as described in U.S. Pat. No. 5,254,783 to Saleh et al., thedisclosure of which is incorporated herein by reference. The catalystcontains amorphous NiO present as a disperse monolayer on the surfacesof a silica support. The support also contains minor amounts of an oxideof aluminum, gallium or indium such that the ratio of NiO to metal oxidepresent in the catalyst is within the range of from about 4:1 to about100:1. The catalyst converts linear butenes to octene products having onaverage less than about 2.6, generally less than 2.0 to 2.4. methylgroups per molecule.

[0041] The NiO catalyst is particularly effective for the dimerizationof butene to form a mixed polymerization product composed mainly ofoctenes. Preferably, the C₄ ⁺OTO will not contain more than 5% by weightof isobutene, because isobutene tends to form products with a highdegree of branching. The desired isobutene concentrations can beachieved by selectivity hydrogenating C₄ ⁺ OTO. The presence ofparaffins in the olefin feed is not generally detrimental, but if theproportion rises above 80% by weight the process becomes uneconomical.

[0042] The oligomerization using a NiO catalyst is carried out in eitherthe liquid or gas phase. Temperature conditions include a temperaturefrom 150° C. to 275° C. and, in the gas phase, a liquid hourly weightfeed rate of butene over the catalyst of from 0.4 hr⁻¹ to 1.8 hr⁻¹,preferably from 0.6 hr⁻¹ to 0.7 hr⁻¹. Where the oligomerization reactionis conducted in the liquid phase and the catalyst is mixed with theolefin, it is preferred that the ratio of olefin to catalyst be in therange of from 2:1 to 8:1, more preferably from 4:1 to 6:1. In caseswhere the oligomerization is conducted under pressure near, at or abovethe critical temperature of the olefin, it is often desirable to insurethat the liquid phase is maintained by carrying out the reaction in thepresence of an inert higher boiling hydrocarbon such as a normalparaffin or cycloparaffin.

[0043] In another embodiment, a ZSM-57 catalyst can be used as anoligomerization catalyst. ZSM-57 provides high product selectivity tooctenes with a decrease in the amount of branching product and crackingof the olefin. Also, the ZSM-57 catalyst exhibits a relatively higherreactivity with pentenes that are also present in C₄ ⁺ OTO. As a result,the yield of nonenes is increased in the process. In fact, additionalpentenes can be added to C₄ ⁺ OTO from an external source to boost theyields of nonene in the process. The oligomerization may take place at atemperature in the range of from 80° C. to 400° C., preferably from 120°C. to 300° C., and most preferably from 150° C. to 280° C., at apressure advantageously in the range of from 2 MPa to 15 MPa, preferablyfrom 5 MPa to 10 MPa, and at an olefin hourly space velocityadvantageously in the range 0.1 hr⁻¹ to 30 hr⁻¹, preferably from 0.5hr⁻¹ to 15 hr⁻¹, and most preferably 0.75 hr⁻¹ to 8 hr⁻¹.

[0044]FIG. 2 depicts separation unit 15 divided into several separationunits 15 a, 15 b, 15 c, 15 d, and 15 e. In one embodiment, separationunits 15 a-15 e can be designed as follows. Separation unit 15 b removesthe pentenes and hexenes 17 b from the higher olefin product 16. Thepentenes and hexenes 17 b can be used as fuel and/or may also bedirected to the higher olefin reaction unit 14. The recycled pentenesand hexenes 17 b can combine with C₄ ⁺ fraction 12 to form additionalnonene and decane, respectively. Separation unit 15 c removes theheptenes 17 c, separation unit 15 d removes the octenes 17 d, andseparation unit 15 e removes the nonene 17 e. Other separation units canbe used to separate the remainder of the higher olefin product. Forexample, it may be desirable to separate the significant amount ofdodecenes from the C₁₀-C₂₀ higher olefin 19 to produce C₁₃-alcohols. TheC₁₀-C₂₀ higher olefin 19 can also be used as chemical feedstock forother commercial value products, such as jet fuel or high qualitysolvents. The separations according to carbon number may be carried outusing methods known in the art as described in Kirk-Othmer, Encyclopediaof Chemical Technology, 4th edition, Volume 20, John Wiley & Sons, 1996,the disclosure of which is incorporated herein by reference.

[0045] Because C₄ ⁺ OTO contains mostly butenes, the product expectedfrom a higher olefin unit will contain primarily octenes (about 70%),dodecenes (about 17%) as well as some nonenes (about 5%) and C₁₆-C₂₀alkenes (about 5%). These percentages will vary depending upon the typeof oligomerization catalyst used and the hydrocarbon feed composition.

[0046] It may, be desirable to produce additional nonene from the higherolefin unit. One way of accomplishing this task is to feed additional C₅olefin to the higher olefin unit. The source of the C₅ olefin may comefrom a steam cracker, or from the small amount produced by the higherolefin unit. Additional C₅ olefin may also be obtained fromcatalytically cracking the higher olefin product such as the heptane andC₁₀ to C₂₀ olefin.

[0047] Following separation of the higher olefin product into thedesired higher olefin components based on carbon numbers, the respectiveseparated higher olefin can be directed to one or more hydroformylationunits. In one embodiment, the octenes and nonenes can be directed tohydroformylation units to produce nonanyl alcohol and decyl alcohol,respectively. The remaining portion of the higher olefin product, thatis, higher olefin with ten or more carbons can be directed to ahydrogenation unit. The hydrogenated products can be used as blendingcomponents to increase the quality of diesel or aviation fuel. A portionof the octene and nonene not directed to the hydroformylation units mayalso be directed to the hydrogenation unit.

[0048] One hydroformulation process that may be used is commonlyreferred to as the oxo-process. In the oxo-process, an olefin reactswith carbon monoxide and hydrogen at elevated temperature and pressurein the presence of a catalyst to produce predominately two isomericaldehydes: a terminal or normal, aldehyde, and an internal, or branched,aldehyde. The position of the formyl group in the aldehyde productdepends upon the olefin, the catalyst, the solvent, and the reactionconditions. Typically, the use of catalysts with strictly encompassingcomplexing ligands, e.g., tertiary phosphines, results predominately inthe formation of the normal aldehyde. In most commercial processes theinitially formed aldehyde product is not isolated. Rather, the aldehydesare further converted to alcohols by a hydrogenation process or by analdolization/hydrogeneration process. Purification of higher molecularweight alcohols usually includes low pressure distillation orseparations involving falling film evaporators.

[0049] A variety of transition metals catalyze the conversion of olefinto aldehydes, but typically only cobalt and rhodium complexes are usedin commercial oxo plants. A commercial oxo process involving aconventional cobalt catalyst may include at least the following steps:hydroformylation, that is, the formation of the aldehyde, removal andrecovery of catalyst, aldehyde refining, hydrogenation, and finallyalcohol refining. In addition, commercial plants may use thealdolization/hydrogenation process to convert the aldehydes to alcohols.Commercial hydroformylations are carried out continuously in either backmixed or tubular stainless steel reactors or in combinations of the two.In the back mixed reactor, the composition of the reaction mixture isconstant and close to that of product. In the tubular reactor, thecomposition changes continually with time because of plug flow throughlong narrow tubes. Reaction conditions vary depending on the olefinfeed, but generally are 100° C. to 180° C. and 20 MPa to 35 MPa. Thepressure used is determined by the catalyst stability at a particularreaction temperature. Catalyst concentrations of about 0.1% to 1% cobaltbased on olefin and liquid residence times of 1 hour to 2 hours arecommon.

[0050] Conversion of crude oxo aldehydes to alcohols is accomplished byheterogenous vapor or liquid phase hydrogenation in fixed bed reactors.Among the metals that have been used as catalysts for thesehydrogenations are copper, nickel, tungsten, cobalt, molybdenum sulfide,and various combination of these metals. Because sulfur poisoning is nota concern in this invention, nickel or cobalt containing catalysts arepreferred. Catalysts frequently are placed on inert supports by reactionof the corresponding metal oxides with hydrogen.

[0051] The hydrogenation of oxo-products are typically carried out at100° C. to 250° C.; the specific conditions are dictated by the catalystbeing used and the desired conversion. The vapor phase process isoperated at low pressures, and the liquid phase process is operated upto pressures of 35 MPa. Internal or external cooling, or both, arerequired to remove heat from the reaction.

[0052] The use of a cobalt carbonyl catalyst modified by organicphosphine ligands can significantly improve hydroformylation selectivityto the more desirable terminal aldehydes, which in turn will most likelylead to terminal alcohols. Although these phosphine modified, cobaltcatalysts are less reactive than uncomplexed cobalt carbonyls, they canbe used at higher reaction temperatures, i.e., 150° C. to 210° C., andlower pressures 2 MPa to 10 MPa. These catalysts are also activehydrogeneration catalysts. As a result, the hydroformylation and much ofthe hydrogenation steps occurs in the same reactor, thus producingpredominately alcohols if the H₂ to CO ratio in the feed synthesis isabout 2 to 1. This single step process, along with a strong preferenceof the catalysts for the reaction at the terminal position of linearolefins makes it possible to prepare alcohols with a high linear tobranched ratio from mixtures of internal and terminal linear olefins.

[0053] The formation of linear aldehydes is also favored by ligandmodified rhodium carbonyl catalysts. Typical complex catalystconcentrations contain from 50 ppm to 150 ppm of rhodium. Additionalinformation on commercial oxo-processes is described in Kirk-Othmer,Encyclopedia of Chemical Technology, 3rd edition, Vol. 16, John Wiley &Sons, pp.637-653.

[0054] The C₄ ⁺ OTO according to this invention is produced in anoxygenate to olefin process. The oxygenate to olefin process uses smallpore, zeolite or non-zeolite molecular sieve catalyst to catalyzeconversion of an oxygenate, such as methanol, to primarily C₂ to C₄ ⁺olefin. Zeolite molecular sieve are complex crystalline aluminosilicateswhich form a network of AlO₂ ⁻ and SiO₂ tetrahedra linked by sharedoxygen atoms. The negativity of the tetrahedra is balanced by theinclusion of cations such as alkali or alkaline earth metal ions. In themanufacture of some zeolites, non-metallic cations, such astetramethylammonium (TMA) or tetrapropylammonium (TPA), are presentduring synthesis.

[0055] Zeolites include materials containing silica and optionallyalumina, and materials in which the silica and alumina portions havebeen replaced in whole or in part with other oxides. For example,germanium oxide, tin oxide, and mixtures thereof can replace the silicaportion. Boron oxide, iron oxide, gallium oxide, indium oxide, andmixtures thereof can replace the alumina portion. Unless otherwisespecified, the terms “zeolite” and “zeolite material” as used herein,shall mean not only materials containing silicon atoms and, optionally,aluminum atoms in the crystalline lattice structure thereof, but alsomaterials which contain suitable replacement atoms for such silicon andaluminum atoms.

[0056] Non-zeolite, silicoaluminophosphate molecular sieves arepreferred for use in connection with this invention. These sievesgenerally comprise a three-dimensional microporous crystal frameworkstructure of [SiO₂], [AlO₂] and [PO₂] tetrahedral units. In general,silicoaluminophosphate molecular sieves comprise a molecular frameworkof corner-sharing [SiO₂], [AlO₂], and [PO₂] tetrahedral units. This typeof framework is effective in converting various oxygenates into olefinproducts.

[0057] It is preferred that the silicoaluminophosphate molecular sieveused in this invention have a relatively low Si/Al₂ ratio. In general,the lower the Si/Al₂ ratio, the lower the C₁-C₄ saturates selectivity,particularly propane selectivity. A Si/Al₂ ratio of less than 0.65 isdesirable, with a Si/Al₂ ratio of not greater than 0.40 being preferred,and a Si/Al₂ ratio of not greater than 0.32 being particularlypreferred. A Si/Al₂ ratio of not greater than 0.20 is most preferred.

[0058] Silicoaluminophosphate molecular sieves are generally classifiedas being microporous materials having 8, 10, or 12 membered ringstructures. These ring structures can have an average pore size rangingfrom about 3.5-15 angstroms. Preferred are the small pore SAPO molecularsieves having an average pore size of less than about 5 angstroms,preferably an average pore size ranging from about 3.5 to 5 angstroms,more preferably from 3.5 to 4.2 angstroms. These pore sizes are typicalof molecular sieves having 8 membered rings.

[0059] Substituted SAPOs can also be used in this invention. Thesecompounds are generally known as MeAPSOs or metal-containingsilicoaluminophosphates. The metal can be alkali metals (Group IA),alkaline earth metals (Group IIA), rare earth metals (Group IIIB,including the lanthanide elements), and the transition metals of GroupsIB, IIB, IVB, VB, VIIB, VIIB, and VIIIB. Incorporation of the metalcomponent is typically accomplished adding the metal component duringsynthesis of the molecular sieve. However, post-synthesis ion exchangecan also be used as disclosed in U.S. Pat. No. 5,962,762 to Sun et al.and U.S. patent application Ser. No. 09/615,526, the disclosures ofwhich are incorporated herein by reference.

[0060] Suitable silicoaluminophosphate molecular sieves include SAPO-5,SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34,SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47,SAPO-56, the metal containing forms thereof, and mixtures thereof.Preferred are SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-44, and SAPO-47,particularly SAPO-17, SAPO-18 and SAPO-34, including the metalcontaining forms thereof, and mixtures thereof. As used herein, the termmixture is synonymous with combination and is considered a compositionof matter having two or more components in varying proportions,regardless of their physical state.

[0061] The silicoaluminophosphate molecular sieves are synthesized byhydrothermal crystallization methods generally known in the art. See,for example, U.S. Pat. Nos. 4,440,871; 4,861,743; 5,096,684; and5,126,308, the methods of making of which are fully incorporated hereinby reference. A reaction mixture is formed by mixing together reactivesilicon, aluminum and phosphorus components, along with at least onetemplate. Generally the mixture is sealed and heated, preferably underautogenous pressure, to a temperature of at least 100° C., preferablyfrom 100-250° C., until a crystalline product is formed. Formation ofthe crystalline product can take anywhere from around 2 hours to as muchas 2 weeks. In some cases, stirring or seeding with crystalline materialwill facilitate the formation of the product.

[0062] The SAPO molecular sieve structure can be effectively controlledusing combinations of templates. For example, in a particularlypreferred embodiment, the SAPO molecular sieve is manufactured using atemplate combination of TEAOH and dipropylamine. This combinationresults in a particularly desirable SAPO structure for the conversion ofoxygenates, particularly methanol and dimethyl ether, to light olefinssuch as ethylene and propylene.

[0063] The silicoaluminophosphate molecular sieve is typically admixed(i.e., blended) with other materials. When blended, the resultingcomposition is typically referred to as a SAPO catalyst, with thecatalyst comprising the SAPO molecular sieve.

[0064] Materials which can be blended with the molecular sieve can bevarious inert or catalytically active materials, or various bindermaterials. These materials include compositions such as kaolin and otherclays, various forms of rare earth metals, metal oxides, othernon-zeolite catalyst components, zeolite catalyst components, alumina oralumina sol, titania, zirconia, magnesia, thoria, beryllia, quartz,silica or silica or silica sol, and mixtures thereof. These componentsare also effective in reducing, inter alia, overall catalyst cost,acting as a thermal sink to assist in heat shielding the catalyst duringregeneration, densifying the catalyst and increasing catalyst strength.It is particularly desirable that the inert materials that are used inthe catalyst to act as a thermal sink have a heat capacity of from about0.05 cal/g-0C to about 1 cal/g-° C., more preferably from about 0.1 toabout 0.8 cal/g-° C., most preferably from about 0.1 cal/g-° C. to about0.5 cal/g-° C.

[0065] The catalyst composition preferably comprises about 1% to about99%, more preferably about 5% to about 90%, and most preferably about10% to about 80%, by weight of molecular sieve. It is also preferredthat the catalyst composition have a particle size of from about 20μ to3,000μ, more preferably about 30μ to 200μ, most preferably about 50μ to150μ.

[0066] Any standard reactor system can be used in the oxygenate toolefin process including fixed bed, fluid bed or moving bed systems.Preferred reactors are co-current riser reactors and short contact time,countercurrent free-fall reactors. Desirably, the reactor is one inwhich an oxygenate feedstock can be contacted with a molecular sievecatalyst at a weight hourly space velocity (WHSV) of at least about 1hr⁻¹, preferably in the range of from about 1 hr⁻¹ to about 1000 hr⁻¹,more preferably in the range of from about 20 hr⁻¹ to about 1000 hr⁻¹,and most preferably in the range of from about 20 hr⁻¹ to about 500hr⁻¹. WHSV is defined herein as the weight of oxygenate, and hydrocarbonwhich may optionally be in the feed, per hour per weight of themolecular sieve content of the catalyst. Because the catalyst or thefeedstock may contain other materials which act as inerts or diluents,the WHSV is calculated on the weight basis of the oxygenate feed, andany hydrocarbon which may be present, and the molecular sieve containedin the catalyst.

[0067] Preferably, the oxygenate feed is contacted with the catalystwhen the oxygenate is in a vapor phase. Alternately, the process may becarried out in a liquid or a mixed vapor/liquid phase. When the processis carried out in a liquid phase or a mixed vapor/liquid phase,different conversions and selectivities of feed-to-product may resultdepending upon the catalyst and reaction conditions.

[0068] The process can generally be carried out at a wide range oftemperatures. An effective operating temperature range can be from about200° C. to about 700° C., preferably from about 300° C. to about 600°C., more preferably from about 350° C. to about 550° C. At the lower endof the temperature range, the formation of the desired olefin productsmay become markedly slow. At the upper end of the temperature range, theprocess may not form an optimum amount of product.

[0069] The pressure also may vary over a wide range, includingautogenous pressures. Effective pressures may be in, but are notnecessarily limited to, oxygenate partial pressures at least 1 psia,preferably at least 5 psia. The process is particularly effective athigher oxygenate partial pressures, such as an oxygenate partialpressure of greater than 20 psia. Preferably, the oxygenate partialpressure is at least about 25 psia, more preferably at least about 30psia. For practical design purposes it is desirable to operate at amethanol partial pressure of not greater than about 500 psia, preferablynot greater than about 400 psia, most preferably not greater than about300 psia.

[0070] The conversion of oxygenates to produce light olefins may becarried out in a variety of catalytic reactors. Reactor types includeconventional reactors such as fixed bed reactors, fluid bed reactors,and riser reactors. Preferred reactors are riser reactors.

[0071] Having now fully described this invention, it will be appreciatedby those skilled in the art that the invention can be performed within awide range of parameters within what is claimed, without departing fromthe spirit and scope of the invention.

What is claimed is:
 1. A method of making olefin derivatives from anoxygenate comprising: contacting the oxygenate with a molecular sievecatalyst to produce a hydrocarbon product containing olefin; separatinga C₄ ⁺ fraction containing four or more carbons from the hydrocarbonproduct; contacting the C₄ ⁺ fraction with an oligomerization catalystto produce a product containing higher olefin and a vent stream; andcontacting a portion of the vent stream with the oligomerzationcatalyst.
 2. The method of claim 1 wherein the C₄ ⁺ fraction comprisesfrom about 80% to about 97% by weight butenes and from about 3% to about20% by weight butanes.
 3. The method of claim 2 wherein the butenescomprise from about 20% to about 40% by weight 1-butene, and from about60% to about 80% by weight 2-butene.
 4. The method of claim 1 whereinthe olefin product comprises less than 20 ppmw by weight of anindividual contaminant, the individual contaminents selected from thegroup consisting of hydrogen sulfide, carbonyl sulfide, and arsine. 5.The method of claim 1 wherein the molecular sieve catalyst is selectedfrom the group consisting of SAPO-17, SAPO-18, SAPO-34, SAPO-35,SAPO-44, SAPO-56, ZSM-5, ZSM-22, ZSM-35, the metal containing forms ofeach thereof, and mixtures thereof.
 6. The method of claim 1 wherein theoligomerization catalyst is selected from the group consisting ofnickel-alkyl aluminum, solid phosphoric acid, nickel-oxide, and ZSM-57.7. The method of claim 1 further comprising contacting a portion of theproduct containing higher olefin with a hydroformylation catalyst. 8.The method of claim 1 further comprising separating octenes from theproduct containing higher olefin and contacting a portion of the octeneswith a hydroformylation catalyst to form nonanyl alcohols.
 9. The methodof claim 1 further comprising separating nonenes from the productcontaining higher olefin and contacting a portion of the nonenes with ahydroformylation catalyst to form decyl alcohols.
 10. The method ofclaim 1 further comprising separating dodecenes from the productcontaining higher olefin and contacting a portion of the dodecenes witha hydrogenation catalyst to form dodecanes.
 11. An olefin compositioncomprising: 60 to 80 percent by weight octene; 2 to 10 percent by weightnonene; and 8 to 25 percent by weight dodecene.
 12. The olefincomposition of claim 11 further comprising 2 to 10 percent by weightolefin having sixteen to twenty carbon atoms.
 13. The olefin compositionof claim 11 wherein the olefin composition comprises a branching numberless than 2.0.
 14. The olefin composition of claim 11 wherein the octenecomprises an average branching number less than 1.4.
 15. The olefincomposition of claim 11 wherein the nonene comprises an averagebranching number less than 1.5.
 16. The olefin composition of claim 11wherein the dodecane comprises an average branching number less than1.8.
 17. The olefin composition of claim 11 wherein the olefincomposition comprises from about 10% to about 50% by weightalpha-olefin.
 18. The olefin composition of claim 11 wherein the octenecomprises from about 60% to about 95% by weight 1-octene.
 19. The olefincomposition of claim 18 wherein the octene comprises from about 5% toabout 30% 2-octene.